Heretofore in the art metal couplings have been welded to the external surface of a metal pipe or tube to enable the metal coupling, when welded to the metal pipe or tube to have a passage drilled therethrough into the metal pipe or tube to provide an inlet or an outlet to or from the interior of the metal pipe or tube so that the metal pipe or tube with the metal coupling welded thereby may be used in the petroleum and petrochemical industries, the chemical industries, in general, and in other industrial uses. Such prior metal couplings have commonly included a generally cylindrical metal body, sometimes having a central internal cavity, and with the body thereof having a relatively steep or sharply inclined beveled base at the bottom of which, and extending centrally thereof, an annular flange has been provided and projects downwardly from the beveled base of the body of the metal coupling. In welding such prior metal couplings to the external surface of a metal pipe or tube the coupling is positioned at the desired and preselected point on the external surface of the metal pipe or tube and welded thereto by applying the weld metal circumferentially around the annular flange on the base of the coupling and filling in with weld metal the annular weld surface area formed and defined by and between the annular flange on the base of the coupling, the side walls of the beveled base, and the external peripheral wall surface of the metal pipe or tube.
However, in the practice of the prior art, as discussed above, it has been found to be very difficult for the welder to form a satisfactory weld joint between the beveled base of the coupling, the annular flange, and the external surface of a metal pipe or tube since in welding such prior metal couplings to a metal pipe or tube the welder must attempt to apply the weld metal circumferentially and uniformly in and around the weld area between the annular flange on the base of the body of the coupling, the beveled surface of the base, and the external surface of the metal pipe or tube, while working with the axis of the metal coupling in a generally horizontal plane and with the welding groove in a vertical plane. This prior practice is difficult for the welder to carry out and has frequently resulted in the welder making unsatisfactory weld joints which have lacked uniformity and have had imperfections therein, including cracks or fissures. Other welding positions could also be used, but they also suffer the same disadvantages. In addition, the prior practice has been expensive from the standpoint of time, labor and materials required in the welding operation because of the sizeable welding groove which must be filled when using this practice.
Similar problems have been experienced heretofore in the prior art of welding other metal attachments, such as solid heavy round metal lugs, to the external surfaces of metal pipes or tubes.